The multi-tap decompression of the self-coupling transformer can accommodate the needs of different load starting and get bigger starting torque, which is a kind of decompression starting method which is often used to start the larger capacity motor. Its biggest advantage is that the start torque is bigger, when the winding tap is at 80%, the starting torque can reach the 64% of the direct start. And can adjust the starting torque through tap. It is still widely used today.